Dental Caries
Dental caries is initiated by the demineralisation of hard tissue on the teeth by organic acids produced from fermentation of dietary sugar by dental plaque odontopathogenic bacteria.
Even though the prevalence of dental caries has decreased through the ‘use of fluoride in most developed countries, the disease remains a major public health problem. The estimated economic burden of treating dental caries in Australia in 1991 was $471 million, being higher than that for other diet-related diseases including coronary heart disease, hypertension or stroke.
In developing countries where the availability of industrialised food products is increasing, prevalence of dental caries is also increasing. Recent studies have highlighted a number of socio-demographic variables associated with the risk of developing caries; high risk is associated with ethnicity and low socio-economic status. The level of high-risk individuals has remained constant even though the overall severity and prevalence of disease in the community has decreased. Dental caries is therefore, still a major public health problem, particularly in ethnic and lower socioeconomic groups. This highlights the need for a non-toxic, anticariogenic agent that could supplement the effects of fluoride to further lower the incidence of dental caries. An agent which would reduce the dose of fluoride required to reduce the incidence of caries would be particularly desirable in view of community anxiety about fluoride, and in view of the fact that fluorosis can develop even at currently used doses.
The food group most recognised as exhibiting anticaries activity is dairy products (milk, milk concentrates, powders and cheeses). U.S. Pat. No. 5,130,123 discloses the component responsible for this anticariogenic activity as casein. However, the use of casein as an anticariogenic agent is precluded by adverse organoleptic properties and the very high levels required for activity.
Preliminary investigations determined that tryptic casein phosphopeptides contributed to the anticariogenic activity and this was made subject of U.S. Pat. No. 5,015,628. In particular, peptides Bos αs1-casein X-5P (f59-79) (SEQ ID NO: 1), Bos β-casein X-4P (f1-25) (SEQ ID NO: 2), Bos αs2-casein X-4P (f46-70) (SEQ ID NO: 3) and Bos αs2-casein X-4P (f1-21) (SEQ ID NO: 4) were disclosed in U.S. Pat. No. 5,015,628 as follows:
(SEQ ID NO: 1)Gln59-Met-Glu-Ala-Glu-Ser(P)-Ile- Ser(P)-Ser(P)-Ser(P)-Glu-Ile-Val- Pro-Asn-Ser(P)-Val-Glu-Gln-Lys79. αs1(59-79) (SEQ ID NO: 2)Arg1-Glu-Leu-Glu-Glu-Leu-Asn-Val- Pro-Gly-Glu-Ile-Val-Glu-Ser(P)-Leu- Ser(P)-Ser(P)-Ser(P)-Glu-Glu-Ser- Ile-Thr-Arg25. β(1-25) (SEQ ID NO: 3)Asn46-Ala-Asn-Glu-Glu-Glu-Tyr-Ser- Ile-Gly-Ser(P)-Ser(P)-Ser(P)-Glu- Glu-Ser(P)-Ala-Glu-Val-Ala-Thr-Glu- Glu-Val-Lys70. αs2(46-70) (SEQ ID NO: 4)Lys1-Asn-Thr-Met-Glu-His-Val-Ser(P)- Ser(P)-Ser(P)-Glu-Glu-Ser-Ile-Ile- Ser(P)-Gln-Glu-Thr-Tyr-Lys21.αs2(1-21)
The preliminary determination of the above phosphopeptides for use in combination with CaHPO4 and hydroxyapatite provided novel peptides having anticariogenic properties. However, subsequent investigations have determined that the Ser(P) cluster sequence motif within the previous disclosed phosphopeptides have the unexpected ability to stabilize their own weight in amorphous calcium phosphate. The ability of the above phosphopeptides and in particular the Ser(P) motif to stabilize amorphous calcium phosphate was quite unexpected and neither disclosed or taught in any publications known to the Applicants. We have now found that the amorphous form of calcium phosphate Ca3(PO4)1.87(HPO4)0.2xH2O where x≧1 stabilised by the casein phosphopeptides is the most soluble, basic form of non-crystalline calcium phosphate and a superior form of calcium phosphate which prevents caries and increases calcium bioavailability. Amorphous calcium phosphate (ACP) must be formed by careful titration of Ca ions (eg CaCl2) and phosphate ions (eg Na HPO4) while maintaining the pH above 7 (preferably 9.0) in the presence of the phosphopeptide. As the ACP is formed, the phosphopeptide binds to the nascent nuclei and stabilises the ACP as a phosphopeptide-ACP complex. Without the phosphopeptide, the ACP will precipitate out of solution and transform within minutes into the most stable calcium phosphate phase, crystalline hydroxyapatite (HA). HA, by being insoluble has limited anticariogenic activity and presents calcium in a poorly bioavailable form. The acidic phase of calcium phosphate CaHPO4, while certainly being more soluble than hydroxyapatite, is poorly bound by the phosphopeptide and poorly localised at the tooth surface and therefore also has limited anticariogenic activity. The unexpected ability of the aforementioned phosphopeptides and in particular Ser(P) cluster motif to stabilize amorphous calcium phosphate was not disclosed or taught in U.S. Pat. No. 5,015,628 and provides for the first time a reliable and effective method of producing a stabilized amorphous calcium phosphate complex having distinct and novel advantages in calcium treatments and delivery. U.S. Pat. No. 5,015,628 does not disclose the unique amorphous calcium fluoride phosphate phase Ca8(PO4)5FxH2O where x≧1 which we have now found to be stabilised by the above phosphopeptides and can be localised at the tooth surface to provide superior anticaries efficacy. This unexpected ability to stabilize amorphous calcium phosphate forms the basis of the instant invention.